Any ritual that’s been around since before we were born seems like it’s always been and will always be, yet they come and go, they change without us ever really seeing it. Birthdays can be a good occasion to see this in action. Birthdays lend themselves to rituals, both big and small. We celebrate every year, but some years we celebrate more than others.

As a society we’ve agreed on some of the birthdays to celebrate big, we’ve almost agreed on others, and we can get downright random on still more. When we start out, every birthday is a big deal. One year, two years, three years, these are still grand milestones, celebrated with almost the same fervor that they were in the days when a child often didn’t make it till age five. So then what ages beyond that? Well, to the kids it’s still a big deal to become a teenager, at least in English speaking countries. In the United States we celebrate the mostly adulthood of eighteen and the full adulthood of twenty-one. And Jack Benny fans get to celebrate being thirty-nine. And celebrate it again, and again.

While we were talking about this, God assured me that the linguistic pattern of numbers ending in “teen” being so close to the ages at which we march our way through puberty is actually less of a coincidence than it might seem, but I don’t know if I’m buying it. In any event, many cultures celebrate a transition from child to at least approximately some form of adulthood at an age that corresponds to puberty. We have Sweet Sixteens, and Confirmations, and Bar Mitzvahs, and Quinceaneras. I imagine that in primitive societies, where we weren’t so desperate to keep our development hidden away in layers of clothes, such celebrations were actually tied to developmental milestones rather than specific years, but we’re oh too sophisticated now to actually admit, as a society, that we notice when boy’s voices change or when girl’s chests expand, or when hair begins to sprout, well, almost anywhere.

We still find ways, though, to celebrate the transitions themselves, the things we do because we’re ready rather than because it’s time. The rite of passage to adulthood used to be the transition from short pants to long pants, now it’s when we stop eating off of the kids’ menu.